I like these threads. Great to hear different opinions on the subject. I knew Danny liked UAD and for good reason. Being a synth kind of guy who is knowledgeable about electronics Jeff weighs in with a good reason to use a solid state based pre amp over  tube ones. If Mike were still here he would likely be going on about the great reasons to buy hardware..remember Mike? What ever happened to him? Mike was also knowledgeable about the inner workings of gear. I kind of miss some of his rants about gear that almost sounded condescending. 
Bat is a tried and true guitarist who only uses the purest of the pure to get those great sounds. Heck, anyone who is using a duo core to record is using about 99% outboard gear or he would choke his cpu, and I don't fault him for that. he knows how to get good tone and how to get a good signal into the computer and it isn't done with a computer lol!
 
AT has some great advice on inexpensive preamps made the good way. He has personally tried and uses many of these boxes. I wouldn't ever feel I had wasted money on any of that mid level gear he recommended.
 
In only using my ears and in listening to recordings I think there is an argument to be made for using an outboard pre of some kind that has good reviews, since all of the best recordings I've heard were done with a decent pre amp but not necessarily a tube pre amp.
 
I just collabed with an acoustic guitarist and he uses a few of those focusrite "lunchboxes" with nice sdc's. I use a mediocre tube pre that I don't drive and he runs rings around my sound. I have to do more to make mine sound good...his already sounds good.Those pres make a difference.
 
I think UAD must be about the best ITB solution from everything I've heard. They represent an investment too though, especially if you buy something like the Apollo. 400 won't kill most people to spend on a pre. Danny makes a good point in that it's destructive, but they tracked years ago, made good albums and none of it could be saved in a computer.
I'm not faulting Danny. Time is money. For something that gets you there and you don't need to jump up and fiddle with knobs why not? You can save everything ITB for later.
 Either way works.